When asked which substance had the most detrimental effect on health -- tobacco, alcohol, sugar or marijuana -- only eight percent identified marijuana.

Fifteen percent responded that sugar was the most harmful, however, while 49 percent said tobacco was the worst and 24 percent said alcohol was the most harmful.

Americans increasingly support legalizing marijuana use. In October 2013, a Gallup poll found that 58 percent of Americans said the drug should be legal, up from 50 percent in 2011 and only 12 percent in 1969.

The new WSJ/NBC poll also found that young Americans read more about legalizing marijuana in the news than they do about the situation in Ukraine or Obamacare. Among adults age 18-35, 57 percent said they had read about marijuana, while only 44 percent said they had read a lot about Obamacare and 39 percent said they read about Russia's invasion of Ukraine.